Time-dependent density functional theory studies of dynamics of hydroxy by proton impact

Using the time-dependent density functional theory and non-adiabatic coupling in molecular dynamics, the reaction dynamics of collisions between energetic proton and hydroxy is studied. The variations in kinetic energy of proton and hydroxy and the motions of electron of hydroxyl and ion before and after collisions are investigated. It is found that when a proton is incident in the direction perpendicular to the molecular axis, it that has lose kinetic energy rebounds, and captures electrons from hydroxy, while the hydroxy that has lost part of electrons gains kinetic energy, and thus translates toward the calculating boundary in the manner of contracting vibration. The larger the kinetic energy of incident proton, the more the number of electrons captured from hydroxy is. Therefore the bond length of hydroxy lengthens, oscillation strengthens, and vibrational frequency decreases. In addition, it is found that the incident direction of proton has a great influence on the dynamic behavior of excitation in a collision process. Considering the case where the proton is incident from different directions, the results show that the larger the kinetic energy of incident proton, the more the lost energy is, and the lost energy is linearly related to the initial kinetic energy of incident proton. For hydroxy, when the incident kinetic energy of proton is less than 25 eV, the kinetic energy gained by the proton is linearly related to the initial kinetic energy, but unrelated to incident direction, while when the initial kinetic energy of incident proton is larger than 25 eV, the increment in kinetic energy of hydroxyl is much larger in the case where the proton is incident along the axis of hydroxyl molecule than in the case where the proton is incident in the direction perpendicular to the axis of the hydroxyl molecule.